NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA/P. Marenfeld
This artistic illustration depicts asteroid 2025 MN45 — the fastest rotating asteroid with a diameter greater than 500 meters ever discovered by science.
The asteroid recently discovered by the Robin Observatory is rotating every 1.88 minutes. Generally, having a rotation faster than 2.2 minutes results in the destruction of the asteroid.
The Vera C. Rubin Observatory discovered the fastest rotating asteroid of which there is record, with more than 500 meters in diameter.
Named 2025 MN45, the 710-meter-long object is located in the main asteroid belt between Jupiter and Mars and completes one rotation every 1.88 minutes. This discovery, along with 18 other rapidly rotating asteroids, represents the first scientific results from the Rubin Observatory’s Legacy Survey of Space and Time (LSST), and was released on January 7, 2026 in the Astrophysical Journal Letters. The data was collected in April and May 2025, during the commissioning of the telescope’s instruments.
The public had a first glimpse of capabilities of Rubin in June 2025, but the 10-year observation campaign begins in 2026.
“The Rubin Observatory, funded by the NSF and the US Department of Energy, will find things that no one even knew they existed“, says Luca Rizzi, director of NSF’s research infrastructure program. “When Rubin’s Legacy Survey of Space and Time begins, this huge rotating asteroid will be accompanied by an avalanche of new information about our Universe, captured every night.”
Under normal circumstances, objects in the asteroid belt tend to rotate at less than 2.2 minutes per rotationin what is known as a rotation barrier. Rotating faster than this often results in the asteroid fragmenting into smaller pieces or splitting into a binary object.
The rotation barrier is determined by several factors, including the proportion of icy and rocky material within an object, its size, and whether the asteroid is a single solid block or a cluster of small fragments. Astronomers believe that “fragment clusters” are the most common type of asteroid, but with its high rotation speed, 2025 MN45 is definitely not one.
“Clearly, this asteroid must be made of a material with very high resistance to stay intact while spinning so quickly,” says lead study author Sarah Greenstreet. “We calculated that it would need a cohesive force similar to that of solid rock.”
Among the other asteroids discovered, second place goes to 2025 MJ71, which rotates almost as fast, at 1.9 minutes per rotation.
Of the 19 fast-rotating asteroids described in the new paper, only one is outside the main asteroid belt. Before Rubin, most known fast-rotating asteroids were near-Earth objects. Rubin’s unique capabilities are enabling detailed observations at greater distances than ever before, and the LSST survey is expected to result in a wealth of new data about the asteroid belt and beyond.
Rubin’s main advantage, besides having the largest digital camera ever built, is that it will monitor the night sky repeatedly, capturing any changes that occur in the sky from one night to the next. These changes are called “transients” and include asteroids (and possibly new planets), but also distant events like supernovae and the dimming or brightening of variable stars. Over ten years, LSST will also create a detailed map of the Milky Way and help astrophysicists understand dark matter by cataloging the sizes of distant galaxies.
